1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
|
/* Copyright (C) 2003 Russ Cox, Massachusetts Institute of Technology */
/* See COPYRIGHT */
/*
* Generic RPC packet multiplexor. Inspired by but not derived from
* Plan 9 kernel. Originally developed as part of Tra, later used in
* libnventi, and then finally split out into a generic library.
*/
#include <u.h>
#include <libc.h>
#include <mux.h>
static int gettag(Mux*, Muxrpc*);
static void puttag(Mux*, Muxrpc*);
static void enqueue(Mux*, Muxrpc*);
static void dequeue(Mux*, Muxrpc*);
void
muxinit(Mux *mux)
{
memset(&mux->lk, 0, sizeof(Mux)-offsetof(Mux, lk));
mux->tagrend.l = &mux->lk;
mux->rpcfork.l = &mux->lk;
mux->sleep.next = &mux->sleep;
mux->sleep.prev = &mux->sleep;
}
void*
muxrpc(Mux *mux, void *tx)
{
int tag;
Muxrpc *r, *r2;
void *p;
/* must malloc because stack could be private */
r = mallocz(sizeof(Muxrpc), 1);
if(r == nil)
return nil;
r->r.l = &mux->lk;
/* assign the tag, add selves to response queue */
qlock(&mux->lk);
tag = gettag(mux, r);
//print("gettag %p %d\n", r, tag);
enqueue(mux, r);
qunlock(&mux->lk);
/* actually send the packet */
if(tag < 0 || mux->settag(mux, tx, tag) < 0 || _muxsend(mux, tx) < 0){
qlock(&mux->lk);
dequeue(mux, r);
puttag(mux, r);
qunlock(&mux->lk);
return nil;
}
qlock(&mux->lk);
/* wait for our packet */
while(mux->muxer && !r->p){
rsleep(&r->r);
}
/* if not done, there's no muxer: start muxing */
if(!r->p){
if(mux->muxer)
abort();
mux->muxer = 1;
while(!r->p){
qunlock(&mux->lk);
p = _muxrecv(mux);
if(p)
tag = mux->gettag(mux, p) - mux->mintag;
else
tag = ~0;
//print("mux tag %d\n", tag);
qlock(&mux->lk);
if(p == nil){ /* eof -- just give up and pass the buck */
dequeue(mux, r);
break;
}
/* hand packet to correct sleeper */
if(tag < 0 || tag >= mux->mwait){
fprint(2, "%s: bad rpc tag %ux\n", argv0, tag);
/* must leak packet! don't know how to free it! */
continue;
}
r2 = mux->wait[tag];
if(r2 == nil || r2->prev == nil){
fprint(2, "%s: bad rpc tag %ux (no one waiting on that tag)\n", argv0, tag);
/* must leak packet! don't know how to free it! */
continue;
}
r2->p = p;
dequeue(mux, r2);
rwakeup(&r2->r);
}
mux->muxer = 0;
/* if there is anyone else sleeping, wake them to mux */
if(mux->sleep.next != &mux->sleep)
rwakeup(&mux->sleep.next->r);
}
//print("finished %p\n", r);
p = r->p;
puttag(mux, r);
qunlock(&mux->lk);
return p;
}
static void
enqueue(Mux *mux, Muxrpc *r)
{
r->next = mux->sleep.next;
r->prev = &mux->sleep;
r->next->prev = r;
r->prev->next = r;
}
static void
dequeue(Mux *mux, Muxrpc *r)
{
r->next->prev = r->prev;
r->prev->next = r->next;
r->prev = nil;
r->next = nil;
}
static int
gettag(Mux *mux, Muxrpc *r)
{
int i, mw;
Muxrpc **w;
for(;;){
/* wait for a free tag */
while(mux->nwait == mux->mwait){
if(mux->mwait < mux->maxtag-mux->mintag){
mw = mux->mwait;
if(mw == 0)
mw = 1;
else
mw <<= 1;
w = realloc(mux->wait, mw*sizeof(w[0]));
if(w == nil)
return -1;
memset(w+mux->mwait, 0, (mw-mux->mwait)*sizeof(w[0]));
mux->wait = w;
mux->freetag = mux->mwait;
mux->mwait = mw;
break;
}
rsleep(&mux->tagrend);
}
i=mux->freetag;
if(mux->wait[i] == 0)
goto Found;
for(; i<mux->mwait; i++)
if(mux->wait[i] == 0)
goto Found;
for(i=0; i<mux->freetag; i++)
if(mux->wait[i] == 0)
goto Found;
/* should not fall out of while without free tag */
fprint(2, "libfs: nwait botch\n");
abort();
}
Found:
mux->nwait++;
mux->wait[i] = r;
r->tag = i+mux->mintag;
return r->tag;
}
static void
puttag(Mux *mux, Muxrpc *r)
{
int i;
i = r->tag - mux->mintag;
assert(mux->wait[i] == r);
mux->wait[i] = nil;
mux->nwait--;
mux->freetag = i;
rwakeup(&mux->tagrend);
free(r);
}
|